Relevant bibliographies by topics / Autoxidative reactions

Academic literature on the topic 'Autoxidative reactions'

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Published: 10 December 2022
Last updated: 28 January 2023

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Journal articles on the topic "Autoxidative reactions"

1

Wolff, S. P., and R. T. Dean. "Glucose autoxidation and protein modification. The potential role of ‘autoxidative glycosylation’ in diabetes." Biochemical Journal 245, no. 1 (July 1, 1987): 243–50. http://dx.doi.org/10.1042/bj2450243.

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Monosaccharide autoxidation (a transition metal-catalysed process that generates H2O2 and ketoaldehydes) appears to contribute to protein modification by glucose in vitro. The metal-chelating agent diethylenetriaminepenta-acetic acid (DETAPAC), which inhibits glucose autoxidation, also reduces the covalent attachment of glucose to bovine serum albumin. A maximal 45% inhibition of covalent attachment was observed, but this varied with glucose and DETAPAC concentrations in a complex fashion, suggesting at least two modes of attachment. The extent of inhibition of the metal-catalysed pathway correlated with the extent of inhibition of glycosylation-associated chromo- and fluorophore development. DETAPAC also inhibited tryptophan fluorescence quenching associated with glycosylation. Conversely, ketoaldehydes analogous to those produced by glucose autoxidation, but generated by 60Co irradiation, bound avidly to albumin and accelerated browning reactions. It is therefore suggested that a component of protein glycosylation is dependent upon glucose autoxidation and subsequent covalent attachment of ketoaldehydes. The process of glucose autoxidation, or ketoaldehydes derived therefrom, appear to be important in chromophoric and fluorophoric alterations. It is noted, consistent with these observations, that the chemical evidence for the currently accepted ‘Amadori’ product derived from the reaction of glucose with protein amino groups is consistent also with the structure expected for the attachment of a glucose-derived ketoaldehyde to protein. The concept of ‘autoxidative glycosylation’ is briefly discussed in relation to oxidative stress in diabetes mellitus.
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Cilliers, Johannes J. L., and Vernon L. Singleton. "Nonenzymic Autoxidative Reactions of Caffeic Acid in Wine." American Journal of Enology and Viticulture 41, no. 1 (1990): 84–86. http://dx.doi.org/10.5344/ajev.1990.41.1.84.

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Cilliers, Johannes J. L., and Vernon L. Singleton. "Nonenzymic autoxidative phenolic browning reactions in a caffeic acid model system." Journal of Agricultural and Food Chemistry 37, no. 4 (July 1989): 890–96. http://dx.doi.org/10.1021/jf00088a013.

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Cilliers, Johannes J. L., and Vernon L. Singleton. "Characterization of the products of nonenzymic autoxidative phenolic reactions in a caffeic acid model system." Journal of Agricultural and Food Chemistry 39, no. 7 (July 1991): 1298–303. http://dx.doi.org/10.1021/jf00007a021.

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Field, J. A., and G. Lettinga. "Treatment and Detoxification of Aqueous Spruce Bark Extracts by Aspergillus niger." Water Science and Technology 24, no. 3-4 (August 1, 1991): 127–37. http://dx.doi.org/10.2166/wst.1991.0469.

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Debarking effluents of the forest industry are severely toxic waste streams due to their high tannin content. The objectives of this study were to evaluate the treatment and detoxification of debarking wastewater with tannin tolerant fungi. For this purpose, Aspergillus niger was cultivated on aqueous bark extracts and the toxicity was assayed utilizing methanogenic bacteria as the test organism. Sterilized aqueous extracts of spruce bark were diluted to 5.2 g COD L−1 (containing 2.7 g tannin COD L−1) in either citrate or tartrate buffer and inoculated with A. niger spores. During four day aerobic fermentations with citrate buffer, the elimination of unfiltered and soluble COD was 28 and 63%, respectively. The apparent yield of biomass averaged 34% of the extract COD; however, 12% of the extract COD was tannins adsorbed on the fungal biomass. The decrease in the tannin concentratio was 50%. According to gel chromatography results, the original oligomeric tannins that resisted biodegradation were those of the highest MW. The toxicity was consequently only partially reduced by the fermentation. During the tartrate buffered fermentations, the pH rose due to the metabolism of the organic acid in the buffer. The rise in pH beyond 6 promoted autoxidative reactions that caused extensive polymerization of the tannins which resisted biodegradation. This resulted not only in an enhanced elimination of the tannins but also in a complete detoxification of the extracts. Similar levels of detoxification could be obtained in sterile un-inoculated extracts by autoxidation alone (raising the pH and aerating the extracts). Likewise, extracts fermented in citrate buffer could be completely detoxified by a subsequent autoxidation treatment. The exclusion peak of the gel chromatograms (MW > 30,000 g mole−1) obtained from the highly autoxidized samples accounted for 53% of the UV absorbance, whereas no exclusion peak was present in the unoxidized extracts. For the biological treatment and detoxification of debarking wastewaters, we recommend the cultivation of tannin tolerant fungi followed by short autoxidation treatments that polymerize the oligomeric tannin fraction resisting biodegradation to non-toxic high molecular weight polymers.
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Ballesteros, Daniel, Hugh W. Pritchard, and Christina Walters. "Dry architecture: towards the understanding of the variation of longevity in desiccation-tolerant germplasm." Seed Science Research 30, no. 2 (June 2020): 142–55. http://dx.doi.org/10.1017/s0960258520000239.

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AbstractDesiccation-tolerant (DT) plant germplasm (i.e. seeds, pollen and spores) survive drying to low moisture contents, when cytoplasm solidifies, forming a glass, and chemical reactions are slowed. DT germplasm may survive for long periods in this state, though inter-specific and intra-specific variation occurs and is not currently explained. Such variability has consequences for agriculture, forestry and biodiversity conservation. Longevity was previously considered in the context of morphological features, cellular constituents or habitat characteristics. We suggest, however, that a biophysical perspective, which considers the molecular organization – or structure – within dried cytoplasm, can provide a more integrated understanding of the fundamental mechanisms that control ageing rates, hence the variation of longevity among species and cell types. Based on biochemical composition and physical–chemical properties of dried materials, we explore three types of the interplay between structural conformations of dried cytoplasm and ageing: (1) cells that lack chlorophyll and contain few storage lipids may exhibit long shelf life, with ageing probably occurring through slow autoxidative processes within the glassy matrix as it relaxes; (2) cells with active chlorophyll may die quickly, possibly because they are prone to oxidative stress promoted by the photosynthetic pigments in the absence of metabolic water and (3) cells that lack chloroplasts but contain high storage lipids may die quickly during storage at −20°C, possibly because lipids crystallize and destabilize the glassy matrix. Understanding the complex variation in structural conformation in space and time may help to design strategies that increase longevity in germplasm with generally poor shelf life.
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Zeng, Meirong, Nadja Heine, and Kevin R. Wilson. "Evidence that Criegee intermediates drive autoxidation in unsaturated lipids." Proceedings of the National Academy of Sciences 117, no. 9 (February 18, 2020): 4486–90. http://dx.doi.org/10.1073/pnas.1920765117.

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Autoxidation is an autocatalytic free-radical chain reaction responsible for the oxidative destruction of organic molecules in biological cells, foods, plastics, petrochemicals, fuels, and the environment. In cellular membranes, lipid autoxidation (peroxidation) is linked with oxidative stress, age-related diseases, and cancers. The established mechanism of autoxidation proceeds via H-atom abstraction through a cyclic network of peroxy–hydroperoxide-mediated free-radical chain reactions. For a series of model unsaturated lipids, we present evidence for an autoxidation mechanism, initiated by hydroxyl radical (OH) addition to C=C bonds and propagated by chain reactions involving Criegee intermediates (CIs). This mechanism leads to unexpectedly rapid autoxidation even in the presence of water, implying that as reactive intermediates, CI could play a much more prominent role in chemistries beyond the atmosphere.
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Veselinović, Aleksandar, Ružica Nikolić, and Goran Nikolić. "Application of multivariate curve resolution-alternating least squares (MCR-ALS) for resolving pyrogallol autoxidation in weakly alkaline aqueous solutions." Open Chemistry 10, no. 6 (December 1, 2012): 1942–48. http://dx.doi.org/10.2478/s11532-012-0125-z.

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AbstractMultivariate curve resolution — alternating least squares (MCR-ALS) has been applied to data collected from UV/Vis spectrophotometric analysis of the autoxidation process of pyrogallol in weakly alkaline aqueous solutions. The MCR-ALS analysis was able to explain the autoxidation kinetics of pyrogallol at pH 7.4 and 8.0, allowing deduction of the pure spectra and concentration changes of different species present throughout the entire process. The autoxidation process at pH 7.4 was found to follow a first-order reaction model, with formation of purpurogallin as the sole and terminal product. Changing the pH to 8.0 not only accelerated autoxidation of pyrogallol to purpurogallin but also introduced a further autoxidation of purpurogallin. At pH 8.0 the process fits a model of two consecutive first-order reactions. The first step is formation of purpurogallin, which reacts in a further autoxidation to form a yellow colored substance, most probably purpurogallin polymer.
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Griesser, Markus, Jean-Philippe R. Chauvin, and Derek A. Pratt. "The hydrogen atom transfer reactivity of sulfinic acids." Chemical Science 9, no. 36 (2018): 7218–29. http://dx.doi.org/10.1039/c8sc02400f.

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Sulfinic acids are characterized to be very good H-atom donors to each of alkyl and alkoxyl radicals. In order to participate in useful radical chain reactions, the sulfonyl radicals must undergo fast propagating reactions to avoid autoxidation, which is surprisingly rate-limited by the reaction of sulfonyl radicals with oxygen.
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Xu, Ruochong, Joel A. Thornton, Ben H. Lee, Yanxu Zhang, Lyatt Jaeglé, Felipe D. Lopez-Hilfiker, Pekka Rantala, and Tuukka Petäjä. "Global simulations of monoterpene-derived peroxy radical fates and the distributions of highly oxygenated organic molecules (HOMs) and accretion products." Atmospheric Chemistry and Physics 22, no. 8 (April 26, 2022): 5477–94. http://dx.doi.org/10.5194/acp-22-5477-2022.

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Abstract. We evaluate monoterpene-derived peroxy radical (MT-RO2) unimolecular autoxidation and self- and cross-reactions with other RO2 species in the GEOS-Chem global chemical transport model. The formation of associated highly oxygenated organic molecules (HOMs) and accretion products are tracked in competition with other bimolecular reactions. Autoxidation is the dominant fate up to 6–8 km for first-generation MT-RO2, which can undergo unimolecular H shifts. Reaction with NO can be a more common fate for H-shift rate constants < 0.1 s−1 or at altitudes higher than 8 km due to the imposed Arrhenius temperature dependence of unimolecular H shifts. For MT-derived HOM-RO2, generated by multistep autoxidation of first-generation MT-RO2, reaction with other RO2 species is predicted to be the major fate throughout most of the boreal and tropical forest regions, whereas reaction with NO dominates in the temperate and subtropical forests of the Northern Hemisphere. The newly added reactions result in an approximate 4 % global average decrease in HO2 and RO2, mainly due to faster self-/cross-reactions of MT-RO2, but the impact upon HO2, OH, and NOx abundances is only important in the planetary boundary layer (PBL) over portions of tropical forests. Predicted HOM concentrations in MT-rich regions and seasons can exceed total organic aerosol predicted by the standard version of the GEOS-Chem model depending on the parameters used. Comparisons to observations reveal that large uncertainties remain for key reaction parameters and processes, especially with respect to the photochemical lifetime and volatility of HOMs as well as the rates and branching of associated RO2 accretion products. Further observations and laboratory studies related to MT-RO2-derived HOMs and gas-phase RO2 accretion product formation kinetics – especially their atmospheric fate, such as gas–particle partitioning, multiphase chemistry, and net secondary organic aerosol formation – are needed.
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Dissertations / Theses on the topic "Autoxidative reactions"

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Walker, John Stuart. "Autoxidation reactions of chlorophyll." Thesis, University of York, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.403864.

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Abou-Zaid, Anas Mamdouh. "On the Prevalence and Role of Addition Reactions in Lipid Peroxidation." Thesis, Université d'Ottawa / University of Ottawa, 2021. http://hdl.handle.net/10393/42411.

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Plasmalogens have been reported to possess antioxidant activity; a paradoxical finding given that plasmalogens often comprise highly oxidizable polyunsaturated fatty acids esterified to the central position of the glycerol backbone. However a reasonable mechanism accounting for plasmenyl lipid activity has yet to be advanced, despite the fact that other monounsaturated lipids including cholesterol and oleate have been extensively studied. Plasmenylcholine was synthesized de novo to resolve its antioxidant activity as well as to carry out mechanistic studies to understand its basis. Autoxidation of a vinyl ether model substrate yielded a kp of 6 M-1 s-1, which affirmed it was as slower than cholesterol. However, corresponding experiments with a deuterated substrate yielded a value of 89 M-1 s-1, questioning the reliability of these studies. Our studies of plasmenyl lipid peroxidation inspired us to look into the mechanism of autoxidation of the monounsaturated lipid, oleate (using LC-MS/MS with APCI+), which was reported to proceed exclusively via H-atom transfer (HAT). Herein we have shown for the first time that oleate epoxides are formed in the autoxidation of the monounsaturated lipid.
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Baum, Sarah L. "Radical reactions of esters relevant to the autoxidation of lubricants." Thesis, University of York, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.341466.

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Fischer, Johannes. "Reaktions- und sicherheitstechnische Untersuchung der partiellen Autoxidation von Cyclohexan in Mikrostrukturen." Doctoral thesis, Universitätsbibliothek Chemnitz, 2011. http://nbn-resolving.de/urn:nbn:de:bsz:ch1-qucosa-70031.

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In dieser Arbeit wird die partielle Autoxidation von Cyclohexan zu Cyclohexanol und Cyclohexanon mit Luftsauerstoff in einem Kapillarrohrreaktor untersucht. Gegenüber dem konventionellen Verfahren wurde die Temperatur auf 180-250°C und der Druck auf 20-80 bar angehoben. Auf diese Weise konnte eine Steigerung der Raum-Zeit-Ausbeute um etwa den Faktor 200 (von 25 kg/m³*h auf ca. 6000 kg/m³*h) erreicht werden. Die Umsätze sind dabei denen der industriellen Anlage vergleichbar. Die Selektivität der partiellen Oxidation zu den Wertprodukten cyclohexanol, Cyclohexanon und Cyclohexylhydroperoxid liegt im Kapillarrohrreaktor mit 80-90 % etwas unter den in der industriellen Anlage erreichbaren Selektivität von ca. 90-95 %. Die Reaktion im Kapillarrohrreaktor wurde auch aus sicherheitstechnischer Perspektive untersucht. Cyclohexan ist in die Explosionsgruppe IIA eingeordnet. Um das System in konservativer Weise zu betrachten, wurde als Stoffsystem Ethen (Referenzgas der Explosionsgruppe IIB) im Gemisch mit Sauerstoff bzw. Lachgas ausgewählt. Es wurde ein Versuchsaufbau konstruiert, mit dem ex möglich war stabile Detonationen zu erzeugen, diese in die Mikrostruktur einzuleiten und deren Ausbreitung und ggf. Austritt aus der Mikrostruktur zu beobachten. Im Versuchsprogramm wurde der Anfangsdruck im Bereich von 0,1 bis 10 bar und der Rohrdruchmesser der eingesetzten Kapillarrohr im Bereich von 0,13 - 1 mm variiert. Es zeigt sich, dass sich stabile Detonationen von stöchiometrischen Ethen/Sauerstoff-Gemischen bei einem Anfangsdruck von 1 bar abs gerade noch durch eine Kapillare mit einem Innendurchmesser von 0,13 mm ausbreiten können. Es wurde aus den Messdaten und theoretischen Betrachtungen eine Kennzahl für die Bewertung von Mikrostrukturierten Bauteilen entwickelt und diskutiert: der maximale sichere Rohrdurchmesser
In this thesis a process is described for the uncatalyzed selective oxidation of cyclohexane with air at high-p, T-conditions in a micro capillary reactor. At 533 K a spacetime-yield of about 6000 kg/(m3 ? h) is reached, which corresponds to a size of 2 m x 2 m x 2 m(8 m3) of the microstructured reactor assuming a capacity of 100000 t/a compared to 500 m3 total reactor volume realized with a cascade of bubble columns of each about 100 m3. Unfortunately, selectivity drops at this temperature below 80 % which is significantly lower than the selectivity in the conventional process. With the help of the Hatta number, mass transfer limitations can be excluded for the micro capillary reactor, whereas the bubble column reactor is weakly limited by the gas/liquid mass transfer of the molecular oxygen. Thus, process intensification by enhancing mass transfer using a microstructured reactor for cyclohexane oxidation with air is quite low. Furthermore a method and its corresponding results are presented for the determination of maximum safe capillary diameters, which may be used to describe the extended range of safe operation conditions for gas phase oxidation reactions in microstructured reactor devices. Sections of stainless steel micro capillaries of different inner diameters are mounted between a primary and a secondary chamber. An explosion is ignited in the primary chamber, where also a deflagration to detonation transition occurs. The propagation of the detonation through the stainless steel micro capillaries is monitored by pressure transducers located between the sections of the micro capillaries. This setup is used in order to determine explosion velocities inside the capillaries, maximum safe initial pressures and corresponding maximum safe capillary diameters. Initial investigations are performed with an ideal stoichiometric mixture necessary for complete combustion of ethene with oxygen respectively ethene and nitrous oxide at room temperature. The measured maximum safe capillary diameters obey an indirect proportionality to the initial pressures. The maximum safe capillary diameter can be estimated on the basis of the lambda/3-rule
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Wilson, David Ian. "Model experiments of autoxidation reaction fouling." Thesis, 1994. http://hdl.handle.net/2429/6900.

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Chemical reaction fouling of heat exchangers is a severe problem in the petrochemicals industry, where deposits can be formed by a wide range of undesirable reactions. Autoxidation has been identified as a prime source of deposit formation in oxygenated process streams and fuel storage systems but the fouling mechanism has not been fuily investigated. The fouling of heat exchangers subject to autoxidative fouling was studied using model solutions of an active alkene, indene, in inert solvents saturated with air. The heat exchangers were operated at moderate surface temperatures (180-250°C) and at turbulent flow velocities. The experiments featured air pressures of 342-397 kPa and heat fluxes of 90-280 kW/m². The effects of chemical reaction rate, surface temperature and flow velocity were investigated and compared with existing chemical reaction fouling models. Chemical initiators were used to eliminate the chemical induction periods observed under ‘natural’ thermal initiation and permitted the study of the chemical reaction rate and surface temperature as separate variables. The chemistry of the physical system and the complex reaction mechanism prevented extensive model development. Two fouling probes were used: an annular probe which allowed visual inspection of deposit formation and a novel tubular heat exchanger constructed during this work which allowed inspection of the deposit in situ after an experiment. The same fouling mechanism was found to generate deposit in both probes. Chemical analyses were developed to monitor the autoxidation reaction during the batch fouling experiments. The results confirmed that fouling was caused by the deposition of insoluble polyperoxide gums generated by the reaction of indene and oxygen. The gums aged on the heat exchanger surface to form complex oxygenated solids which were not easily removed. These results confirmed the hypotheses of Asomaning and Watkinson (1992). The kinetics of indene autoxidation was studied in a separate series of semi-batch stirred tank experiments. The rate of formation of polyperoxides was influenced by the solvent nature, temperature, oxygen concentration and mode of initiation. The aromatic polyperoxides exhibited limited solubility in aliphatic solvents. The kinetics of indene autoxidation could not be described by the schemes reported in the literature and were found to be subject to oxygen mass transfer effects. The fouling resistance behaviour was controlled by conditions in the bulk fluid. The initial, linear fouling rate decreased with increasing flow velocity and increased with bulk reaction rate and surface temperature. A simple fouling model, involving generation of deposit in the reaction zone next to the heat transfer surface and an attachment factor related to the mean fluid residence time, was fitted to the experimental data. Once the solubility limit was reached, the fouling resistance showed increasing rate behaviour, caused by the deposition of globules of insoluble gum. The effect of an antioxidant on the fouling process was studied. The efficiency of the antioxidant, di-t-butyl-4-methylphenol, was found to be severely reduced under the enhanced thermal conditions in the heat exchanger. Simulated ageing experiments were performed to investigate the fate of polyperoxides exposed to the enhanced temperatures on the heat exchanger surface. The studies confirmed that the insoluble polyperoxide gums undergo ageing processes after deposition.
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Xue, Zhong-Fen, and 薛仲芬. "Kinetics and reaction mechanism of autoxidation of benzyl alcohol catalyzed by tetraacetonitrile copper(I) complex." Thesis, 1990. http://ndltd.ncl.edu.tw/handle/96311558215755583317.

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7

Fischer, Johannes. "Reaktions- und sicherheitstechnische Untersuchung der partiellen Autoxidation von Cyclohexan in Mikrostrukturen." Doctoral thesis, 2010. https://monarch.qucosa.de/id/qucosa%3A19532.

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In dieser Arbeit wird die partielle Autoxidation von Cyclohexan zu Cyclohexanol und Cyclohexanon mit Luftsauerstoff in einem Kapillarrohrreaktor untersucht. Gegenüber dem konventionellen Verfahren wurde die Temperatur auf 180-250°C und der Druck auf 20-80 bar angehoben. Auf diese Weise konnte eine Steigerung der Raum-Zeit-Ausbeute um etwa den Faktor 200 (von 25 kg/m³*h auf ca. 6000 kg/m³*h) erreicht werden. Die Umsätze sind dabei denen der industriellen Anlage vergleichbar. Die Selektivität der partiellen Oxidation zu den Wertprodukten cyclohexanol, Cyclohexanon und Cyclohexylhydroperoxid liegt im Kapillarrohrreaktor mit 80-90 % etwas unter den in der industriellen Anlage erreichbaren Selektivität von ca. 90-95 %. Die Reaktion im Kapillarrohrreaktor wurde auch aus sicherheitstechnischer Perspektive untersucht. Cyclohexan ist in die Explosionsgruppe IIA eingeordnet. Um das System in konservativer Weise zu betrachten, wurde als Stoffsystem Ethen (Referenzgas der Explosionsgruppe IIB) im Gemisch mit Sauerstoff bzw. Lachgas ausgewählt. Es wurde ein Versuchsaufbau konstruiert, mit dem ex möglich war stabile Detonationen zu erzeugen, diese in die Mikrostruktur einzuleiten und deren Ausbreitung und ggf. Austritt aus der Mikrostruktur zu beobachten. Im Versuchsprogramm wurde der Anfangsdruck im Bereich von 0,1 bis 10 bar und der Rohrdruchmesser der eingesetzten Kapillarrohr im Bereich von 0,13 - 1 mm variiert. Es zeigt sich, dass sich stabile Detonationen von stöchiometrischen Ethen/Sauerstoff-Gemischen bei einem Anfangsdruck von 1 bar abs gerade noch durch eine Kapillare mit einem Innendurchmesser von 0,13 mm ausbreiten können. Es wurde aus den Messdaten und theoretischen Betrachtungen eine Kennzahl für die Bewertung von Mikrostrukturierten Bauteilen entwickelt und diskutiert: der maximale sichere Rohrdurchmesser.
In this thesis a process is described for the uncatalyzed selective oxidation of cyclohexane with air at high-p, T-conditions in a micro capillary reactor. At 533 K a spacetime-yield of about 6000 kg/(m3 ? h) is reached, which corresponds to a size of 2 m x 2 m x 2 m(8 m3) of the microstructured reactor assuming a capacity of 100000 t/a compared to 500 m3 total reactor volume realized with a cascade of bubble columns of each about 100 m3. Unfortunately, selectivity drops at this temperature below 80 % which is significantly lower than the selectivity in the conventional process. With the help of the Hatta number, mass transfer limitations can be excluded for the micro capillary reactor, whereas the bubble column reactor is weakly limited by the gas/liquid mass transfer of the molecular oxygen. Thus, process intensification by enhancing mass transfer using a microstructured reactor for cyclohexane oxidation with air is quite low. Furthermore a method and its corresponding results are presented for the determination of maximum safe capillary diameters, which may be used to describe the extended range of safe operation conditions for gas phase oxidation reactions in microstructured reactor devices. Sections of stainless steel micro capillaries of different inner diameters are mounted between a primary and a secondary chamber. An explosion is ignited in the primary chamber, where also a deflagration to detonation transition occurs. The propagation of the detonation through the stainless steel micro capillaries is monitored by pressure transducers located between the sections of the micro capillaries. This setup is used in order to determine explosion velocities inside the capillaries, maximum safe initial pressures and corresponding maximum safe capillary diameters. Initial investigations are performed with an ideal stoichiometric mixture necessary for complete combustion of ethene with oxygen respectively ethene and nitrous oxide at room temperature. The measured maximum safe capillary diameters obey an indirect proportionality to the initial pressures. The maximum safe capillary diameter can be estimated on the basis of the lambda/3-rule.
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8

Klewicki, J. Kenneth. "The Kinetics of Redox Reactions of Mn(II) and Mn(III) in Aqueous Systems: Homogenous Autoxidation of Mn(II) and the Formation and Disappearance of Mn(III) Complexes." Thesis, 1996. https://thesis.library.caltech.edu/5074/9/Klewicki_jk_1996.pdf.

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The kinetics of manganese redox reactions are important for understanding redox cycles in natural waters. This study examined the kinetics of the homogenous oxidation of Mn(II) and formation and disappearance of Mn(III) complexes.

The oxidation of Mn(II) was studied to determine the homogenous oxidation rate in the absence of solid surfaces and biological activity. Experiments were conducted at 35, 45, 50, and 60°C. The pH was 8.0. The reaction solution was prepared so that at no time during the experiment was the solubility product of any solid phase exceeded. Oxidized Mn was measured using leuco crystal violet dye reagent. Measurable rates were observed for the 45, 50, and 60°C experiments. An Arrhenius expression was fitted to the rates in order to extrapolate to 25°C. The second order rate constant for the rate expression

-d[Mn(II)]/dt = k⋅[Mn(II)⋅[O2]

was calculated to be 6.9 ± 1.6 x 10-7 M-1s-1.

The kinetics of disappearance of Mn(III) complexes from aqueous solution were studied. Complexes of pyrophosphate (P2O74-), ethylenediaminetetracetate (EDTA), and citrate (CIT) were synthesized from MnO4- and a Mn(II) salt in a 1:4 ratio in the presence of excess ligand. Concentrations of Mn(III) complex were monitored spectrophotometrically. Experiments were conducted in the pH range of 6 to 9 for pyrophosphate and citrate and 3 to 9 for EDTA. The total manganese concentration was varied between 0.5 and 1.0 mM. Ligand concentrations were varied from 0.5mM to 200mM. Experiments were also conducted to examine the effects of oxygen, light, and ionic strength. Oxygen had a significant effect on only the citrate complex; ionic strength affected only the EDTA complex. Light was found to be insignificant in all cases.

The Mn(III)P2O7 complex was found to disappear from solution relatively slowly providing the ligand was in at least ten-fold excess. Disappearance time scales were on the order of 107 s. The Mn(III)EDTA complex reacted rather rapidly with time scales on the order of 104 s. There were at least two Mn(III)EDTA complexes, a protonated one more stable at low pH and an unprotonated one more stable at high pH. The pKa of the complex appeared to be approximately 5.3. The rate of disappearance of the Mn(III)EDTA had a fractional dependence on pH, probably indicative of an unknown pH dependent intermediate in the decomposition of the complex. The rate was found to increase with increased EDTA, indicating that the rate limiting step was an outer sphere electron transfer from Mn(III)EDTA to an excess EDTA. The rate law for the reaction above pH 6 was found to be

-d[Mn(III)EDTA]/dt = k⋅[H+]0.31⋅[EDTA]1.35⋅[Mn(III)EDTA]

The Mn(III)CIT complex was found to undergo a redox cycle. The Mn(III)CIT complex was reduced, forming Mn(II). The Mn(II) was then oxidized in the presence of oxygen to re-form the Mn(III) complex. Both pH and ligand concentration were found to have fractional orders in the rate expression, largely due to the competition between the reduction and the oxidation and possibly complicated by radicals formed by the reaction.

The dissolution of MnOOH by pyrophosphate, EDTA, and citrate was studied. A MnOOH solid was synthesized by oxidizing Mn(II) with hydrogen peroxide at elevated temperatures and high pH. The solid was identified by X-ray diffraction to be β-MnOOH, with some contamination by Mn3O4. Throughout the dissolution process samples were removed by pipette and filtered. The filtrate was analyzed spectrophotometrically for the presence of Mn(III) complexes and total Mn. The solids captured on the filter were analyzed by an iodine titration technique, coupled with formaldoxime measurements to determine the average oxidation state of the solids. The effects of pH and ligand concentration on rates were examined.

Pyrophosphate was found to dissolve the Mn(III) solids nonreductively, producing the Mn(III) complex in solution. The dissolution reaction rate was dependent on approximately the half power of [H+], possibly indicative of a surface binding ligand binding on the surface. No dependence on the ligand concentration was found down to a ligand:Mn ratio of 10:1, probably indicative of surface site saturation by ligand.

EDTA was found to dissolve the solids reductively with no Mn(III) solution species being observed. The dependence on [H+] was approximately one half order, possibly indicative of a surface binding.

Citrate dissolved the MnOOH solids in what appeared to be two steps. There seemed to be an initial stage of nonreductive dissolution, followed by a reductive dissolution. The rate and duration of the two different stages depended on pH. The dependence was slightly greater than first order in [H+], possibly indicating the reaction becomes controlled by reactions of the radicals produced by oxidation of the citrate.

This study has shown that Mn(III) complexes can be formed in pH conditions relevant to natural waters. These complexes can be formed either through oxidation of Mn(II) by strong oxidants in the presence of stabilizing ligands or by dissolution of Mn(III)-containing solids by stabilizing ligands. Once formed, the lifetime of these complexes will depend on the nature of the ligand and chemical characteristics of the aquatic environment. If the ligand does not rapidly reduce Mn(III) these complexes can be powerful mobile oxidants which could significantly affect the local redox environment.

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"Synthesis of nordihydroguaiaretic acid (NDGA) analogues and their oxidative metabolism." Thesis, 2015. http://hdl.handle.net/10388/ETD-2015-06-1915.

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Nordihydroguaiaretic acid (NDGA), is a naturally-occurring lignan isolated from the creosote bush (Larrea tridentata). The aqueous extract of this shrub, commonly referred to as Chaparral tea, was listed in the American pharmacopeia as an ethnobotanical used to treat tuberculosis, arthritis and cancer. Other documented traditional applications of creosote bush extract include treatment for infertility, rheumatism, arthritis, diabetes, gallbladder and kidney stones, pain and inflammation among many others. In spite of the numerous pharmacological properties, NDGA use has been associated with toxicities including hepatotoxicity in humans. Previous studies in our group showed that oxidative cyclization of NDGA (a di-catechol) at physiological pH forms a dibenzocyclooctadiene that may have therapeutic benefits whilst oxidation to ortho-quinone likely mediates toxicological properties. In order to investigate the structural features responsible for pharmacological and toxicological properties, a series of NDGA analogues were designed, synthesized and characterized for the purpose of studying their oxidative metabolism. Literature procedures were modified to successfully prepare seven lignan analogues via multi-step synthesis. In our effort to understand the mechanisms of NDGA intramolecular cyclization, the prepared analogues were incubated under previously established conditions where NDGA autoxidized to yield the dibenzocyclooctadiene derivative. We also evaluated the stability of the analogues under the conditions of this study. Furthermore, we evaluated bioactivation potential of the prepared analogues with a goal of eliminating reactive metabolite liability through rational structural modification. We incubated NDGA and its analogues in rat liver microsomes (RLM) in the presence of glutathione as a nucleophilic trapping agent. Standards for comparison were generated by performing glutathione trapping experiments with chemical and enzyme oxidation systems. The potential of the dibenzocyclooctadiene lignan 2 derived from NDGA under physiological conditions to contribute to toxicological properties via reactive metabolite formation was also evaluated. Glutathione conjugates were detected by electrospray ionization-mass spectrometry (ESI-MS) scanning for neutral loss (NL) 129 Da or 307 Da in positive ion mode or precursor ion (PI) scanning for 272 Da in negative ion mode and further characterized by liquid chromatography–tandem mass spectrometry (LC–MS/MS) or in a single LC-MS run using multiple reactions monitoring (MRM) as a survey scan to trigger acquisition of enhanced product ion (EPI) data. We determined that NDGA autoxidation at pH 7.4 is dependent on substituents and/or substitution pattern on the two aromatic rings. In particular, spontaneous intramolecular cyclization to a dibenzocyclooctadiene required a di-catechol lignan, raising the possibility that o-Q formation may not be necessary for cyclization to occur. Cyclization was significantly inhibited in the presence of excess GSH which supports the involvement of free radicals as opposed to o-Q in the intramolecular cyclization process. The mono-catechol analogues A1 and A4 underwent oxidation to o-Q but no evidence of cyclization was found implying that electrophilic substitution cannot account for NDGA cyclization. The phenol-type analogues were oxidatively more stable in comparison with the catechol-type analogues at pH 7.4. The results demonstrate that electrophilic substitution makes no contribution to the intramolecular cyclization process and that a radical mediated process accurately describes the situation for NDGA. Oxidative metabolism and bioactivation studies on NDGA and its analogues revealed that reactive metabolites formation is dependent on substitution and/or substitution pattern of the aromatic rings. Cytochrome P450-mediated oxidation of NDGA and its catechol-type analogues yielded electrophilic intermediates which reacted with GSH. The GSH mono-conjugates were identified as ring adducts derived from o-Q although the position at which the GSH binds to the aromatic rings could not be determined. We also found that NL 129 or 307 scanning in positive ionization mode has potential diagnostic utility in distinguishing between aromatic and benzylic GSH conjugates although further studies may be required for validation. We found no evidence of p-QM either directly or via isomerization of o-Q intermediates suggesting that o-Q is the major reactive toxicophore responsible for reactive metabolite mediated toxicities associated with NDGA use. In addition, we demonstrated that the NDGA-derived dibenzycyclooctadiene lignan (cNDGA 2) undergoes P450-mediated oxidation to a reactive metabolite which might have toxicological implications. There was no evidence of P450-mediated oxidation to reactive metabolites for the phenol-type NDGA analogues. It is concluded that structural modification efforts should focus on phenol-type analogues to potentially enhance the safety profile of NDGA.
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Book chapters on the topic "Autoxidative reactions"

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Gundermann, Karl-Dietrich, and Frank McCapra. "Autoxidation Reactions." In Reactivity and Structure: Concepts in Organic Chemistry, 19–32. Berlin, Heidelberg: Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-71645-4_3.

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Kashimura, N., J. Morita, S. Nishikawa, and Z. Kumazawa. "Autoxidation and DNA Cleavage Reaction of Glycated Proteins." In The Maillard Reaction in Food Processing, Human Nutrition and Physiology, 449–54. Basel: Birkhäuser Basel, 1990. http://dx.doi.org/10.1007/978-3-0348-9127-1_52.

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Morita, J., and N. Kashimura. "Involvement of Monosaccharide Autoxidation in DNA Glycation Under Physiological Conditions." In The Maillard Reaction in Food Processing, Human Nutrition and Physiology, 505–10. Basel: Birkhäuser Basel, 1990. http://dx.doi.org/10.1007/978-3-0348-9127-1_61.

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Sakurai, T., and M. Nakano. "Generation of Superoxide During an Autoxidation of Glycated Protein: Participation in Phospholipids Peroxidation." In The Maillard Reaction in Food Processing, Human Nutrition and Physiology, 493–98. Basel: Birkhäuser Basel, 1990. http://dx.doi.org/10.1007/978-3-0348-9127-1_59.

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Matsuoka, Ariki, and Keiji Shikama. "Aplysia Myoglobin: Involvement of Two Kinds of Carboxyl Groups in the Autoxidation Reaction." In Structure and Function of Invertebrate Oxygen Carriers, 153–59. New York, NY: Springer New York, 1991. http://dx.doi.org/10.1007/978-1-4612-3174-5_21.

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Kawakishi, Shunro, and Koji Uchida. "Autoxidation of Amadori Compounds in the Presence of Copper Ion and its Effects on the Oxidative Damage to Protein." In The Maillard Reaction in Food Processing, Human Nutrition and Physiology, 475–80. Basel: Birkhäuser Basel, 1990. http://dx.doi.org/10.1007/978-3-0348-9127-1_56.

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Kissner, Reinhard. "Reaction Steps in Nitrogen Monoxide Autoxidation." In NOx Related Chemistry, 335–54. Elsevier, 2015. http://dx.doi.org/10.1016/bs.adioch.2014.10.002.

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FÁBIÁN, ISTVÁN, and VIKTOR CSORDÁS. "METAL ION CATALYZED AUTOXIDATION REACTIONS: KINETICS AND MECHANISMS." In Advances in Inorganic Chemistry, 395–461. Elsevier, 2003. http://dx.doi.org/10.1016/s0898-8838(03)54008-9.

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Partenheimer, Walt. "The Metal/Bromide Autoxidation of Hydrocarbons. An Extraordinarily Versatile and Flexible Method for the Oxygenation of Hydrocarbons." In Catalysis of Organic Reactions, 307–17. Routledge, 2017. http://dx.doi.org/10.1201/9781315138855-28.

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Kurata, Tadao, Noriko Miyake, and Yuzuru Otsuka. "Autoxidation Mechanism of Reductones and its Significance in the Maillard Reaction." In The Maillard Reaction in Foods and Medicine, 419. Elsevier, 2005. http://dx.doi.org/10.1533/9781845698447.8.419a.

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Conference papers on the topic "Autoxidative reactions"

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Kandrac, Morgan, and Karen Schaich. "Epoxides are major products in oxidation of methyl oleate and linoleate and their triacylglycerols." In 2022 AOCS Annual Meeting & Expo. American Oil Chemists' Society (AOCS), 2022. http://dx.doi.org/10.21748/wbbv6226.

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Lipid autoxidation poses a significant problem for stabilizing sensory quality, nutritional value, and chemical safety of lipid containing foods. Peroxide value and volatile carbonyls are the most measured markers to assess oxidation, but products such as epoxides and alcohols are now being identified and quantified in foods. The mechanisms and conditions under which other products form are poorly understood, particularly how lipid structure and oxidation conditions affect reaction pathways, products, and rates. This research paper aims to show how number of double bonds affects oxidation product formation, how oxidation temperature affects reaction rates and product formation and decomposition, and how open or closed packaging systems affect reaction rates.Methyl oleate and methyl linoleate were autoxidized neat and incubated at 25, 40, or 60 °C for various incubation periods. Class assays for quantification of oxidation products included the following: conjugated dienes by UV absorbance at 233 nm; peroxide value by reaction with TPP; epoxide value by reaction with diethydithiocarbamate; soluble carbonyls by reaction with 2,4-dinitrophenylhydrazine. Direct separation of oxidation products was performed using NP-HPLC with detection and quantitation by UV and Corona Charged Aerosol (CAD) detection. Alternate autoxidation products competed with the formation of hydroperoxides in both autoxidizing oleate and linoleate. Epoxides were found to be the dominant product in oleate autoxidized at 25 C, reaching a maximum value of 69.2 mmol/mol lipid, while peroxide value reached a maximum of 23.71 mmol/mol lipid. Epoxides were also found to be a major product in linoleate autoxidation reaching a maximum value of 357.5 mmol/mol lipid at 25 C, while peroxide value reached a maximum of 357.1 mmol/mol lipid. For both oxidized oleate and linoleate, rate of epoxide formation competed with that of hydroperoxides, demonstrating that alternate reactions are active and important in directing the reaction rates and product distributions of autoxidizing lipids.
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Issaadi Halima, M., J. Csábi, K. Németh, and A. Hunyadi. "Comparative HPLC and CE studies on the formation of 20-hydroxyecdysone metabolites from base-catalyzed autoxidation and Fenton reaction." In GA 2017 – Book of Abstracts. Georg Thieme Verlag KG, 2017. http://dx.doi.org/10.1055/s-0037-1608260.

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Jones, E. Grant, Walter J. Balster, and James M. Pickard. "Surface Fouling in Aviation Fuels: An Isothermal Chemical Study." In ASME 1995 International Gas Turbine and Aeroengine Congress and Exposition. American Society of Mechanical Engineers, 1995. http://dx.doi.org/10.1115/95-gt-045.

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Surface fouling in aircraft fuel lines that results from autoxidation of aviation fuel remains a serious and very complicated problem. This area has been studied using two Jet-A fuels, POSF-2827 and POSF-2980. The results of a series of dynamic experiments conducted in a single-pass, tubular heat exchanger operated at very slow flow rates under near-isothermal conditions are reported herein. Such studies, by minimizing complications resulting from fluid dynamics and heat flow, constitute a simpler global approach to the chemistry of fouling. The basis for the selection of experimental test conditions is discussed, and data from measurements of dissolved oxygen and surface deposition as a function of fuel stress duration are presented. The effects of parameters such as reaction temperature, tube diameter, experimental test time, and fuel dopants are considered.
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